Apparatus for electrically butt-welding tubing



. July 15, 1924. 1,501,782

G. v. JOHNSTON I APPARATUS FOR ELECTRICALLY' BUTT WELDING TUBING FiledOct. 4. 4920 8 sheets-sheet. 1"

I Infant? July 15, 1924; *1,so1,1s2 G. v'.- JOHNSTON AFPARATUS FORELECTRICALLY BUTT WELDING TUBING Filed Oct. 4, 1920 s Sheets-Sheet 2 1liq 1m 14 WKMA July 15, 1924. 1.501,?82

G. v. JOHNSTON APPARATUS FOR ELECTRICALLY BUTT WELDING TUBING Filed Oct.4, 1920 8 Sheets- Speet 5 July 15, 1924. 1,501,782

G. v. JOHNSTON -A-FPARATUS ELECTRICALLY BUTT WELDING TUBING I Filed Opt.4. 1920 8 Sheets-Sheet July 15, 1924.

G. V. JOHNSTON APPARATUS FOR ELECTRICALLY BUTT WELQING TUBING FiledDct.4, L920 8 Sheets-Sheet 5 M l m w w w W m h M L z: rm WM M J a. yr H. T H9 vw M G. V. JOHNSTON APPARATUS FOR ELECTRICALLY BUTT WELDING TUBING 8Sheets-Sheet 6 Filed Oct. 4;, 1920 Armless July 15,. 1924.

APPARATUS FOR ELECTRICALLY BUTT WELDING TUBING Filed-Oct. 4, 1920 aSheets-Sheet v G. v.- JOHNSTON i A July -15, 1924. 1,501,782

G. V. JOHNSTON APPARATUS FOR ELEGTRICALLY BUTT WELDING TUBING Filed on.4, 1920 8 Sheets-Sheet-8 Imfe n15;

GWIEWX g Patented July 15, 1924.

GUST-AVE V. JOHNSTON, OF CHICAGO, ILLINOIS, ASSIGNOR,

TO THE ELYRIA BY MESNE assremrmvrs,

IRON AND STEEL COMPANY, A CORPORATION OF OHIO.

APPARATUS FOR ELECTRIGALLY BUTT-WELDING TUBING.

Application filed October 4, 1920. Serial No. 414,408.

To all whom it mag/ concern:

Be it known that I, GUSTAYE V. JOHNS- TON, a citizen of the UnitedStates, residing at Chicago in the county of Cook and State of Illinois,have invented certain new and useful Improvements in Apparatus forElectrically Butt-Welding Tubing, of which the following is aspecification.

My invention relates to apparatus for electrically butt-welding tubing,and in some of its aspects constitutes an improvement upon the apparatusset forth and claimed in my co-pencling application Serial No. 302,392filed June 29, 1919.

In the butt-welding of tubing by electricity, and more especially so ineffecting the weld on tubing that is moving at a relatively high rate ofspeed (as was first made possible, I believe, by the practice of themethod or use of the apparatus set forth in my aforesaid application)proper control of the amount of, and the manner of application of, thecurrent are matters of prime importance in the maintenance of thewelding condition. In commercial practice it is not only important thatcontrol of the current shall be exercised by' the operator, but it isvery desirable that such control shall be promptly applicable, shall beof a character to give both wide variation and very close regulation,and shall not require the stopping of the operation of the ma: chine. Ofcourse where the same machine is intended for use in welding tubing ofdifferent gauges or thicknesses, with accordant changes incurrent-demand, wide variation in current supply is a necessity,

and'further, many conditions are encountered in pract1ce,-such, amongothers, as changes in the predetermined speed of tube- 1 travel,variation in condition or composition 'of the tube stock, and perhapsother factors of more" obscure nature,that call for compensatory.variation of the current condition (sometimes in the midst of anoperating run) to maintain a desired adequacy of the weld and theavoidance of stock-burning and in these regards the regulation must bevery close for satisfactory results.

My present invention has for one of its objects to provide a simple,efiicient and desirable apparatus for securing and maintaining, subjectto variation at will and for very close regulation,- the proper currentsupply to the welding electrodes in a ma- 'which I have found to chineof the character described. Another object of my invention is to providean im- I proved transformer suitable for the work described and kindredpurposes. Other and further objects will become apparent to thoseskilled in the art from the following description taken in conjunctionwith the accompanying drawings wherein I have shown a single embodimentof my invention be commercially practical and desirable.

In the drawings, Fig.1 is an illustration of diagrammatic charactershowin portions of a-completed'tube-forming and welding apparatus; Fig.2 is a side elevation with parts broken away on a larger scale; Fig. 3is a tranverse section on lihe 3-3 of Fig. 2; Fig. 4 is afragmentary-detail of a transformer secondary; Fig. 5 is a tra-nversesection through the transformer and regulator; Fig. 6 is a longitudinalfragment thereof; Fig. 7 is a section on line 7-7 of Fig. 6; Fig. 8 is asection on line 88 of Fig. 7; Fig.9 is a wiring diagram; and Fig. 10 isamodified wiring diagram.

10 indicates, diagrammatically, a mechanism for presenting a steel tube,having an open butt seam, to the welding throat that is formed by rollerelectrodes 11 and 12 and tube-supporting means, as roller 13; thesethroat elements being. in non-contacting relation electrically, butmechanically forming an almost complete circular compressionpass throughwhich the tube is fed with the electrodes straddling the seam cleft, andfrictionally rotating the electrodes in its passage. The tubing a may beeither pushed or'pulled through the throat, and may either be pro-formedin lengths or formed in continuous fashion from'flat stock as itapproaches the welding throat. The supporting roller 13 may bepositively driven or frictionally turned by the tubing, variations inthese and other particulars being dictated by circumstances that do notconcern the embodiment of the present invention.

For illustrative simplification of a single construction, thefragmentary mechanism 10 may be regarded as typifying a power drivenapparatus for forming a tube and feeding the tube-formed stock throughthewelding throat (in which case the roller 13 need have no ower-shaftconnection) and the feeding mec anism. should be geared to impart arelatively high speed to the work.

section through a While the speed of tube-propulsion may be and, in myexperience, should be, varied in accordance with the thickness andcomposition of the tube-stock (although maintained substantiallyconstant for any given character of stock) this factor of speed ofprogtube-supporting steel roller 13, preferably ress of the tubing isnot unimportant and has material bearing on my present invention in someof its aspects. I have found in practice that mild steel tubing, of,say, an inch diameter and .035 thickness may effectively be welded at arate of 80 feet per minute and upwards, and'that high-carbon steeltubing, hot rolled from old rail stock and of a thickness averagingabout .110, may be welded at the high rate of 20 feet or more perminute. It will be realized that where alternating current is used (asI- have used it) of the usual 60-cycle frequency, say,

very appreciable tube-progress takes place during the intervals betweenattainment of maximum heating effect due to successive currentalternations, and therefore it is of great moment, on the one hand, soto regulate the current that the temperature of the metal at theseam-cleft is raised very rapidly, to assure the attainment of weldingheat and completion of the weld, and yet, on the other hand, so tocontrol the current as to minimize lateral spreading of the hightemperature zone in the stock and prevent burning thereof at or near theseam-cleft. I have found that I am able to produce excel lent results inthe matter of current regulation and consequent temperature control, ina machine of the character described, as well as to better theperformance of the transformer itself by the employment of devicescombined as hereinafter described.

The transformer shown has a plurality of primary coils associated with asingle-turn, multiple-section secondary, withthe primary coils suitablyconnected and controlled by multiple point switches capable of cuttinginto or out of service numerous coilturns but at a small number perswitch-step. For the desired regulation these switches are connectedtogetherfor coincident operation to cut in or cut out correspondingturns of their respective coils in unison and I prefer that there be aswitch for every coil. These primary coils are preferably arranged forready connection in different relations-in series, or multiple-series orseries-multiple, to accord with the voltage supplied to the primarycoils from the power circuit. This may be done in the initial settingup. of the transformer, as a matter of permanent wiring, or as hereafterdescribed control switches may be provided for changing the character ofthe coil connected readily. Furthermore, I preferably construct thetransformer in a manner suitable to minimize voltage drop or losses inthe secondary and its connected parts and to afford a de:

nonmagnetic, as of manganese-steel, is mounted to rotate on a'fixedhorlzontal axis in the base frame 14, and has formed there-.

in a nearly semi-circular groove that is struck on a radius slightlyless than the radius of the formed but unwelded tube. The transformersecondary carries the brackets 19 in which the roller electrodes 11 and12 are rotatably mounted. These electrodes, I prefer, are quite large,are rigidly connected for synchronous rotation on a horizontal axis, andare jointly grooved supplementally to the grooving of roller 13.

The curvatures of the grooves in the electrode-couple and roller shouldbe made to accord with a tube-perimeter somewhat smaller than that whichthe tube-stock presents when its confronting seam-edges are merelypressed together, but, since it is desirable to minimize the burr formedin welding the edges, this undersizing of the tubepass or throat shouldbe rather slight. The softening of the metal at the seam-cleft by theheat developed by the passage of the current therethrough permits theapplied pressure to reduce slightly the diameter of the tube as it isbeing welded in its passage through the throat.

The transformer frame, in the construction shown, has frame plates 24:and 25 between which the laminae of the core 26 are clamped, the corebeing herein shown as of the ordinary figure 8 shape. A bottom plate 27is provided between which and the plate 25 the single-turn secondary 29is insulatedlysecured. The spaced sections, 30 of the secondary, splitand insulate at their bottoms, are connected at their lower ends withthe two electrode-carrying bases or brackets 19 that have projectingflanges and cars 32 and 33 which are suitably insulated and clampedbetween the plates 25 and 27 the transformer frame structure being heldtogether by vertical bolts 34, and secured in a yoke 35 suitablypositioned in the machine frame.

Fibre saddles 37 (Fig. 5) spanning between the brackets 19, support theprimary coils 38 thatare adequately spaced with respect to, andinsulated from, the secondar sections and the core, for ventilation, eacof these primary coils being preferably made of a single ribbon or flatwire, and each coil having a large number of taps 39 to its superposedturns, preferably atap to' each .turn for approximately the outer halfof the total. Illustratively, if thirtyfive turns be used there may be,say, seventeen taps. Each tap 39 runs to a different contact point of aswitch 40, there being a switch for each coil although, as shown in Fig.8, these switches are preferably arranged in pairs for mechanicalsimplification. Each switch is arranged to control the serviceconnections ofits appropriate coil, that is'to say, to vary the numberof turns of said primary coil included in the service circuit, and theseseveral switches are arrangedfor operation in common (and in thepreferred form shown in unison) by a regulator-handle, so assimultaneously (and also equally, in the preferred form shown) to varythe number of'turns in service in the affected coils. The movable switchelements, as shown, are controlled from a common .handle or wheel 41disposed in position to be easily accessible to the operator. With sucharrangement, permitting the uniform variation for all primary coils ofthe number of turns in service, it will be seen that local actionis'minimized and the distribution of effect of the primary current isalways uniform. v

Specifically, the transformer frame carries brackets 42 for theregulator shaft 43 on which the movable switch elements 44 are fastened,each of these movable elements being double faced to serve the twoopposing switches. Thus, each movable switch arm 44 is oppositelysocketed as at 45 for'a pair of contact shoes 46 for two switches,

each pressed outwardly by springs 47 for constant engagement with aring-contact 48, and selective connection with the spaced tapterminalcontacts 49. These fixed contacts are carried by insulating cups orshell-sections 50 bolted to ether in pairs and all secured to a top ar51 fastened to the brackets 42. An index finger 52 near the hand wheelindicates the number of'coils cut into or. out of service, and a sna-over friction-latch 53, carried by this 'nger, tends to hold the switchelement always in a contacting position with respect to some tapterminal; Preferably the contact shoe slips from pointto point withoutlosing contact with one until after it has engaged the next, so that theprimary circuit is not broken. The frame-brackets have bosses 54to-carry the clamps 55- for bus rods, 56, 56', to which the power wiresare connected, and the coils may be connected with these busbars, ininitially connecting up the transformer, by clamp-terminals 57. Ofcourse, the number of primary coils and turns thereon may be varied,butto facilitate utilization of the transformer in connection withdifferent commercial voltages I referabl make the number of primary cois a mult1- ple of four.. Sixteen 1s a desirable number, where connectionwith power circuits of from 110 V. to 440 V. is contemplated, but fordiagrammatic purposes I have not illusconnected in multiple or series,or seriesmultiple in the circuit. Thus, diagrammatically, in Fig. 9,the. coil groups are'in parallel; the innermost turn of the righthandcoil being connected'at 58 to the busbar 56 while the switch-ring 48 isconnected at 59 to the innermost turn of the next coil, and so onthroughout the series group shown as 3 coils, the last switch of thegroup having its contact-ring 48 wired as at 60 to the bus-bar 56. Thebus-bars are served from a line through main switch 4, Fig. 1, convenientlyaccessible to the operator. In practice I have satisfactorilyconnected up the transformer to 've between four and five volts(measuref across the secondary bases) with all coils in service and haveemployed a regulation giving between two an onl SFhere variability ofconnection of the transformer-coil-groups is desired, enabling them tobe connected at will in series or series-multiple, as well as in themultiple relation heretofore described, I meet this desideratum by theprovision of switches additional to the rotary regulator-switches 40,thereby furthering the capability of the machine to meet widely varyingconditions such as stock changes ranging from very thin to very thickstock. In Fig. 10 I diagram a construction for taking care of fourgroups (A, B, C and D) of coils, although of course more or lessgroupsmay be provided for, and more coils than the two may be used ineach (or any) grou The variableconnections are control ed byfourswitch-groups, a", b, b; 0, a; and d; the six switch blades beingshown as mechanically connected by a connector-linkE that may moveblades a, b, c and d across respectiv groups of'three contacts. Thislink may have lost-motion pin-and-slot engagements c with blades b and0' to lose one step of rightward movement, blades 1) .and 0' having onlytwo contacts (leftward and center); Wire 58 (as in Fig. 9) connects therig t coil of group A with bus-bar 56and w1re-59 connects ring 40 to theinnermost turn of the next coil 38, but the connection from the ring ofthe leftward regulator section of group A to the bus-bar 56 .is madethrough-wire 60, blade a, left contact therefor and wire 60'. Coil groupB has its wires 58 and 60 respectively connected to blades 6, b, theleftward contacts of which res tively are connected with bus-bars 56 an56' by wires 58" and 60". Coil group C has connections in the samearrangement as group B, .(the connection shown being via 58, 0, 58 and60, 0', 60) while group D has wire 60 connected direct with bar 56 andwire 58 connected with switch (2, left contact therefor and wire' 58 tobus-bar 56'. Thus in the relation indicated in Fig. 10 the coil groupsare in multiple, as in Fig. 9. If, however, link E be thrown over onestep, the coil groups are brought into series-multiple with groups A, Bin one par allel; groups C, D in another and these two parallels inseries; and when the-link is moved a second step all coils are throwninto series. The first step of link-movement displaces only fourswitches a, b, 0 and d to meet their middle contacts, switches b and 0remaining in connection with their leftward contacts by virtue of thelostmotion joints 6. The four middle contacts referred to are connectedby wire f, so that from bus-bar 56 current flows through the two coilgroups A and B in parallel to wire 56 and thence through the two groupsC and D in parallel to bus-bar 56. The sec-' ond step brings all bladesto their rightward contacts, and through respective connections g, g andg between right contacts of switches a, b; b, c; and 0', d, all coilsare ,series connected between bus-bars 56 and 56. This supplementaryswitch arrangement'may be disposed-in a housing It mounted on framepiece 51 of the transformer, as shown in Fig. 1, with the handle ofswitch link E conveniently accessible.

The special construction and facility of arrangement as above describedis advantageous in these particulars, among others:

The division of the primary windings intoa rather large number of rathernarrow coils properly spaced, makes for rapid and satisfactoryheatdissipation and permitsthe use of small control-units or switches, whilethe use of flat or ribbon like wire in single strand pan-cake windingfacilitates the connection and compact placement of the ,many tap-offsfrom the different turns and so accommodates the wiring to the bestrequirements of the compact, rather .small switches that I provide.Further, and more importantly perhaps, the subdivision of theprimary-current conductor into the small coils and the provision of thelike'number of regulator switches (especially with the latter connectedin. multiple-series as shown in Fig. 9) so reduces the current handledby each switch-blade that the short-circuited current, which is inducedwhen a switchblade passes from one fixed contact to the next, is sosmall as to cause no trouble. And additionally, the variability of theconnection increases the range of efiective regulation.

Of course, in the operation of the apparatus losses occur in thesecondary and, by reason of its connection to the electrodes, it ismanifestly desirable both to minimize these losses and to provide meansto dissipate the heat engendered in the secondary and its connectionsand indirectly to cool the primary coils. To these ends I prefer toconstruct the secondary and to connect the electrodes therewith asfollows:

The secondary sections shown are watercooled and are disposed in theclosest connection, but detachable relation, to the base or bracketmembers. These brackets, too, are water-cooled; are equipped withadequate ball-bearings for supporting the electrodes; and are mostintimately connected for conductivity with the roller electrodes, thelatter being, (as in my previous machine) also water-cooled. Thus, eachsecondary sec-' tion has a hollow center 30 with provisions forconnecting the bottoms of its legs respectively to water supply andeduction headers h, these sections having transverse feet 61 at thebottom thereof, each forming a right-angle at the heel and an acuteangle at the toe, so that pairs of said sections, stood in transversechannels of the bases or brackets 19 may be jointly secured in place andin most intimate pressure contact with the bases by dove-tail blocks 63screwed to the bases (see Fig. 6). Each bracket 19 has below its solidtop a water circulation space 65 overlain by a detachable cover plate66, and these spaces are connected with the water-flow headers. Eachsuch bracket carries near its outer side a ball bearing 67 to receivethe hub 68 of the corresponding electrode 11 or 12, each electrodehaving a boss 69, and on these bosses there bear a very large number oftangentially-disposed contact brushes 70 that are fixedly secured inring sectors or arcs 71 bolted as at 72 to the bracket structure. Iprefer that the ringclamping bolts 72 shall work in slightly diagonalconvergent slots 7 3 in the brackets so that as the brushes wear theirsectors may be adjusted a little closer to ether and the brushes turneddown, if need e.

As in my prior machine,-the pair of electrodes, bolted together, andsuitably insulated from each other at 74, provide an interior 'waterspace for suitable connection with the headers. With the low voltagesused, water-filling of the electrode space seems to have no appreciableshort-circuiting effect.

While I have herein described in some detail a single embodiment of myinvention which I believe to be specifically advantageous and desirablesome of the refinements of which I may claim for their specificadvantage, it will be understood by those skilled in the art that manchanges may be made in the precise embo iment of my inventionv withoutdeparture from the spirit tlliereof and within the scope of the appendedc aims.

electrodes and opposed tube support, forming a welding throat, analternating-current transformer having its secondary connected with theelectrodes and having a plurality of primary coils in a circuitexcluding said secondary, a plurality of switches respectivelycontrolling the number of service-turns of different primary coils, andmeans for operating said switches.

2. In a tube welding machine, the combi:

nation of means, including seam-straddling electrodes and opposing tubesupport, forming a welding throat, an alternating-current transformerhaving its secondary terminals electrically connected with theelectrodes and having a plurality of primary coils grouped in multipleseries in a circuit excluding said secondary, a plurality of switchescontrolling the service-turns of primary coils respectively in theseveral groups, and means for operating said switches in common.

3. In a tube welding machine, the combination of means, includinseam-straddling electrodes and opposing tu ing a welding throat, analternating current transformer having asin le-turn seconda with itsterminals electrica y connected with the electrodes and having aplurality of pri- 1 mary coils grouped in multiple series in a circuitexcluding said secondary, a plurality of switches connected with, andcontrolling the service-turns of, a like plurality of primary coils inone series-group, and means common to said switches for operating them.

4. In a tube welding machine, the combination of means, including a tubesupport and seam-straddling electrodes, for rapidly passing, exertingressure upon, and supplying current to, utt-seamed tube 1 stock, atransformer having its secondary connected to the electrodes and havinga plurality of'primary coils in a circuit excluding said secondary andeach havin a plurality of turns that are tapped, an a regulatorcomprising a plurality of multiple-point switches, with the points ofeach switch connected with the taps of a respectively corresponding coilto cut in or'cut out coil-turns, and means for operating said switchesin common. v

5. In a tube welding machine, the combination' with means, includingtube supporting and feeding means and seam-straddling electrodes, forrapidly passing, exerting pressure upon, and applying current to,butt-seamed tube stock; means for supplying closely-regulated current oflow voltage and high amperage to said electrodes, comprising analternating current transformer having a sin le-turn secondary connectedto theelect es and including e support, 'forma number of parallel spacedsections, a plurality of primary coils in a circuit excluding saidsecondary and respectively located 1n the interspaces between saidsecondary sections, and regulating means for cutting in and out turns ofa plurality of said primary coils in unison.

6. In a tube welding machine, the combinationwith means, including tubesupporting and feeding means and seam-straddlingelectrodes, for rapidlypassing, exerting pressure upon, and applying current to, butt-seamedtube stock; means for supplying closel -regulated current of low voltageand big amperage to said electrodes, comprising an alternating currenttransformer having a secondary connected in circuit with the electrodesand including a number of parallel spaced sections, a plural ity ofprimary coils respectively located in the interspaces between saidsecondary sections and connected in a circuit excluding said seconda andregulating means for cutting in an out sequentially a;plurality of turnsof all of said respective primary coils in unison.

7 In a tube welding machine, the combination with means, includingseam-straddling electrodes and opposed tube support, forming a weldingthroat; a transformer having its secondary connected with the electrodesand formed in'apluralit of aced parallel sections, and havmg a p uralltyof rimary coils arranged in the interspaces between said sections; of aregulator comprising a shaft extending in proximity to all the primarycoils, switch blades on said shaft, one for each coil, switch contactsfor said respective blades, completing a switch for each coil, saidrespective switch. contacts connected with a plurality of turns oftheappropriate coil, and means for turning said shaft whereby to operatethe switches in iilmison equally to affect all of the primary c0 s.

8. In a machine of the character described, the combination ofelectrodes; a transformer, having its secondary terminals con- .nectedwith said electrodes and formed in a plurality of spaced sections, andhaving a plurality of primary coils each arranged in an interspacebetween secondary sections, and having a frame; a shaft rotatablymounted on said transformer frame; a

plurality of switches through which said and a transformer having itselectrodecarrying secondary divided into spaced sections and its pluralprimary coils arranged in the spaces between the secondary sections, ofa regulator comprising. a plurality of switches, each for a primarycoil, said switches being arranged in pairs and having movablecontact-carrying arms, each common to a pair of switches, and havingrespective fixed contacts that are connected to spaced-apart points ofthe appropriate primary coils, and an operating shaft carrying saidmovable contact arms for operating all of the switches in unison.

10. In a machine of the character described the combination withtube-supporting means and seam-straddling electrodes forming a weldingthroat, of an alternating current transformer having a secondaryconnected with the electrodes and having a plurality of primary coilseach formed in a pancake winding of flat wire, and having taps fromnumerous of its turns; and a regulator comprising a plurality ofswitches, each for a primary winding and each having fixed contactsconnected with taps of the appropriate primary winding and each having amovable blade arranged toretain connection with one fixed contact untilafter it has made connection with the next, and means for operating saidswitches.

11. In a machine of the character described, the combination of weldingelectrodes, an alternating current transformer having a single-turnsecondary connected with said electrodes and having a primary windingconsisting of a plurality of coils, and switch means to connect saidcoils in different electrical relations at will.

12. In a machine of the character described, the combination of weldinelectrodes, an alternating current-trans ormer having a single-turnsecondary connected w thsaid electrodes and having. a primary windingconsisting of a plurality of coils, and switch'means to vary at will thenumber of service-turns of certain of said coils.

I3. In a machine of the character described, the combination of weldingelectrodes, an alternating current transformer connected therewithhaving a primary windng comprising a plurality of groups of coils, thecoils of each group being in series, and switch means for connectingsaid groups at will in multiple or series-multiple.

14. In a machine of the character described, the combination of w'eldinelectrodes, an alternating current trans ormer connected therewithhaving a primary winding comprising a lurallty of groups of coils, thecoilsof eac group being'in series,

and switch means forconnecting said groups.

at will in multiple or series.

I I 15. In a 'machine of the character I described, the combination ofwelding electrodes, an alternating current transformer connectedtherewith havinga primary winding comprising a plurality of groups ofcoils the coils of each group being in series, an switch means forconnecting said groups at will in series or series-multiple.

16. In a machine of the character described, the combination of weldingelectrodes, an alternatingccurrent transformer connected therewithhaving a primary winding comprising a plurality of groups of coils, thecoils of each oup being inseries, and switch means for connecting saidgroups at will, in multiple, series, or seriesmultiple. I

17. In a machine of the character described the combination of weldingelectrodes, an alternating current transformer therefor having a primarywinding comprising a plurality of coils, switch means to connect saidcoils in different group relations and other switch means operable, to

vary the number of service-turnsof coils in each group in common.

18. In a machine of the character described in combination of weldingelectrodes, an alternating current transformer thereof having a primarywinding GOIII- prising a plurality of coils, switch means to connectsaid coils in different "groups relations and other switch meansoperable to vary the number of service-turns of all coils in unison.

19.- In a machine of the character described, the combination of theframe, tube supporting means therein, electrodes separated from, butcooperating with said tubesupportingv means to form a welding throat, analternatin current transformer having hollow secon ary-terminals orbrackets in which said electrodes are mounted for rotation and withwhich said electrodes make electrical connection, and means forcirculating a cooling medium through and in direct contact with themetal of said hollow terminals. j I 20. In a machine of the characterdescribed, the combination of a frame, tube supporting means therein,electrodes separated from but cooperating with said tube supportingmeansto form a welding throat, an alternating current transformer havinga plurality of secondary sections each of single open-loop form ofhollow construction, terminal brackets upon which said secondarysections are set, said brackets affording bearing for and havingprovision for electrical connection with said electrodes, each saidbracket comprising a hollow casting open at its face and a base platedetachably secured thereto for covering the opening, means for securingthe secondary sections upon said brackets, said means extending intoandaccessible from the interior of said brackets, means for supplyingcooling fluid to the interiors of the brackets and the secondarysections, and primary coils interposed between the secondary section. I

21. In a machine of the characterdescribed, the combination of meansforming a tube-pass and comprising tube supporting means and cooperatingroller electrodes, an alternating current transformer comprisingbrackets affording bearing for said elecs trodes and having means forelectrical connection with the later, secondary sections having theirbases detachably mounted in said brackets and arranged in parallel,spaced relation, and primary coils arranged in the interspaces betweenthe secondary sections.

22. In a machine of the character described, the combination ofelectrodes, a transformer having secondary sections each of singleopen-loop form, terminal brackets wherein said sections are seated inspaced relation, said brackets affording bearing for and havingprovisionfor electrical connection with said electrodes, and means fordetachably clamping the section-bases in the brackets.

23. In a machine of the character described, the combination ofelectrodes, a transformer having separate oke-shaped secondary sectionseach having oot-enlar ements, terminal brackets having means ormechanical and electrical connection with said electrodes and havinslots to receive the section-feet to position the sections in parallel,spaced relation, clamping blocks connected with said brackets betweenand engaging the section feet, and primary ooils disposed in the spacesbetween said secondary sections.

24. In a machine of the character described, the combination of rollerelectrodes, a transformer, secondary-terminal brackets having, neartheir outer surfaces, ball-bearings, and carrying, near theirinner-surfaces, tangentially converging contact brushes, said electrodeshaving hub portions engaging said bearings and boss-portions receivingthe contact brushes.

GUSTAVE vi JOHNSTON.

